(1) Field of the Invention
The present invention relates to an apparatus and a method for controlling a speed change of an automatic transmission of an automobile, and more particularly, to a technique of carrying out a down-shift on the basis of a vehicle running resistance and a drive force.
(2) Related Art of the Invention
Conventionally, in order to speedily carry out a down-shift with respect to an increase of a running resistance such as an incline resistance, there has been proposed a speed change control apparatus for an automatic transmission (see Japanese Unexamined Patent Publication No. 7-239021), which is constructed in a manner of making a comparison between the running resistance and a drive force, and forcibly carrying out a down-shift when the drive force is less than the running resistance.
As described above, with the construction of carrying out a forced down-shift on the basis of the comparison between the running resistance and the drive force, for example, when an uphill incline changes from +4% to +8%, an increase in the uphill incline is made a trigger, a forced down-shift is carried out.
The insufficient drive force is speedily compensated according to the aforesaid forced down-shift; however, the forced down-shift is carried out regardless of a driving operation of a driver. Therefore, there has arisen a problem that the driver feels the aforesaid down-shift like a sudden speed change.